The sensor of the meter pulses in the direction of the product surface. There, they are reflected back and received by the sensor. The meter measures the time t between pulse transmission and reception. The meter uses the time t (and the velocity of sound c) to calculate the distance D between the sensor membrane and the product surface: D = c*t/2
As the device knows the empty distance H from a user entry, it can calculate the level as follows: L = H - D
An integrated temperature sensor compensates for changes in the velocity of sound caused by temperature changes.
Calibration
Enter the empty distance H and the span F to calibrate the device.